1. Field of the Invention
The present invention relates to a wiring harness which conveys electrical signals representing measurements made at a first location to a measuring instrument remotely located from such first location.
2. Background of the Invention
It has been common practice for many years to measure the physiological functions of the human body to determine the health of a patient. This is generally accomplished by attaching electrodes to specific areas so that the functions of particular organs of the body can be determined. For example, it has been common practice to measure electrocardiogram (EKG) signals from a body.
The normal practice for obtaining readouts to form an electrocardiogram has been to adhere electrodes to different portions of the body and then connect each electrode to a wire, which will terminate in an EKG trunk connector. The connector is plugged into a trunk cable which is then attached to the remote measuring electronic instrumentation. The measuring instrument to construct the traditional EKG waveforms for display amplifies the potential differences between pairs of electrodes.
The number of electrodes that may be attached to the human body varies. It depends on the detail of information required from the hardware. In normal clinical practice, between three and ten electrodes may be placed on the body.
It is clear, however, that as the quantity of electrodes is increased, the quantity of EKG wires may become unmanageable. Such wires may often become tangled with themselves. This poses a problem, which can be made worse in a critical care setting, such as in an operating room or intensive care unit of a hospital, where the EKG wires are only one group of many wires going from an electronic instrument such as a monitor to the patient. In this setting, all the cables can get tangled with each other. Accordingly, a lot of skilled nursing time is spent merely untangling the cables.
Previous attempts at improving manageability of EKG wiring harnesses by minimizing tangling include fabricating a plurality of wires in a flat membrane-like multiwire cable where the width of the cable changes with the distance from the measuring instrument. In such an arrangement, each wire of the multiwire cable has its own electrode which provide only a fragile connection and complicates locating the electrode at the correct location on the patient's body.
Also, different types of electrodes have been used to obtain better adherence to the human body. Each such electrode must include a means for connecting that electrode to the monitoring equipment. For example, suction cups have been used as well as self-adhesive cloth containing a metal electrode. In both of these cases, a contact in the EKG wire is then snapped on the metal electrode attached to the self-adhering element. The force required to snap the electrode onto and remove the electrode from the EKG wiring harness can lead to failure in the wiring harness and/or damage to the connector itself.
Another problem is the presence of other electronic equipment, with associated wires and sensors, in close proximity to the EKG wiring harness. Such equipment can cause severe electro-magnetic interference (EMI). In known arrangements, EMI is minimized by using shielded wire, such as coaxial cable, to connect the EKG monitor to the sensors.
Furthermore, in an operating room, electrocautery devices are typically used. An electrocautery device is a surgical knife which is supplied with a relatively high level of radio frequency (RF) current so that blood vessels and other tissues are cauterized and sealed immediately upon cutting. The RF current may be picked up by one EKG sensor, coupled to that sensor wire's shield through the cable capacitance, then to other shields of other sensor wires at a common connection point. The relatively high level of RF current is then supplied to the other EKG sensors where it can cause burns on the patient at the EKG sensor site. Prior art arrangements minimize the conduction of RF energy among the EKG sensor wire shields by providing high potential electrical isolation (on the order of several kilovolts) at least at RF frequencies between respective shields of EKG sensors.
A wiring system which can provide a wiring harness which minimizes the potential for tangling with itself and other wiring harnesses, which minimizes the potential for damage due to connecting and disconnecting the wiring harness to the electrodes, which provides EMI protection and prevents RF burning due to the use of electrocautery devices, is desirable.